Overall objectives of the study are: the purification, characterization, and comparison of alkaline phosphatase (AP) isoenzymes induced in chicks by vitamin D and glucocorticosteroids; the determination of the relationship of these isoenzymes to the mechanism of antagonism between these substances with respect to intestinal calcium transport. In this same vein is the objective to determine the role of vitamin D induced intestinal Ca-ATPase (as an AP isoenzyme) in intestinal calcium and/or phosphate transports.